Roger Thompson, senior engineering specialist with the Aerospace Corporation in Virginia, said modeling of Tiangong 1's re-entry by monitors in the USA had been highly accurate, leaving him feeling "great" about their predictions.
A defunct Chinese space lab plunged through Earth's atmosphere on Monday, breaking apart as it headed towards a watery grave in the South Pacific, Beijing said.
"Most of the devices were ablated during the re-entry process". When the Mir space station was launched in 1986, Soviet space authorities boosted Salyut 7 to a higher orbit and abandoned it there.
At an altitude of 37 to 43 miles, debris will begin to turn into "a series of fireballs", which is when people on the ground will "see a spectacular show", he said.
Tiangong-1 had officially stopped sending data and entered its final phase of life on March 16, a statement issued recently by the China Manned Space Engineering Office said.
Tiangong-1, was the size of a school bus and weighed eight and a half tons.
Anything that did make it through the atmosphere "will be at the bottom of the ocean by now", he added.
Female astronaut Wang Yaping delivered a lecture from space lab to students back on Earth.
A Chinese spaceflight engineer, however, denied earlier this year that it was out of control. The Long March 5 failed on its second test flight in 2017, and a third demonstration is scheduled for late this year before Chinese officials commit to putting more valuable payloads on the rocket, including a lunar sample return probe, a Mars rover and pieces of the Chinese space station.
The United States Air Force 18th Space Control Squadron, which tracks and detects all artificial objects in Earth's orbit, said it had also tracked the Tiangong-1 in its re-entry over the South Pacific. "It had helped us accumulate precious experience in constructing space station", said Huang Weifen, Deputy Chief Designer of the Astronaut Center of China.
"There's a specific location in the ocean known as the spacecraft graveyard where nations try and put down into", he said.
Tiangong-1 was launched in 2011 to carry out docking and orbit experiments.
The "vast majority" of the craft burnt up on re-entry, at around 8:15 a.m. (0015 GMT), the authority said in a brief statement on its website, without saying exactly where any pieces might have landed. It said it plans to assemble it in space in 2020 and will become fully operational in 2022. Some debris fell in sparsely populated western Australia, causing no problems except for a $400 fine for littering.